Title: 0514 - Effect of Varying Cantilever Lengths for Screw Retained FPDs


Kenneth Kurtz (Presenter)
Montefiore Medical Center

Jason Griggs, University of Mississippi
Ikuya Watanabe, Nagasaki University
sitki dogus, Montefiore Medical Center
mark danbe, Montefiore Medical Center


Objectives: To evaluate the effects of cantilever length in screw retained fixed cantilevered prostheses.

Methods: Twenty-one 3-unit screw retained cantilever FPDs were cast in high palladium alloy (Advantage, Jensen Industries) in three groups. In all groups an engaging cast-to component was incorporated into the distal implant unit; the proximal unit received a non-engaging component. In group A, the cantilever distance was 5.0mm. In groups B and C, the cantilever distances were 7.5mm and 10mm respectively. Specimens were subjected to accelerated lifetime testing using step-stress fatigue and the results were statistically evaluated. Two previous investigations by the same group have established the investigative protocols and have identified trends which may have clinical relevance. (Dogus, 2011) Samples were attached to internally connected 3.5x13mm implants (RePlant, Implant Direct), torqued to 35Ncm in accordance with the manufacturer’s specifications, and embedded into epoxy resin (Epoxycure, Beuhler). Samples were tested with a 2Hz sine wave and 0.1 min/max load ratio. Load amplitude started at 1.8 N and increased by 1.8 N every 60 cycles until failure. Log rank statistic was utilized to evaluate level of statistical significance with regard to number of cycles and amount of force at failure between survival curves using one-way ANOVA.

Results: In the Reference Group, Group A, the mean number of cycles to failure was 89,055 (SD=7,533). Mean axial force at failure was 1,331N (SD=112N). In Group B, these numbers were 84,105 (SD=6,061), 1,257N (SD=90N), and in Group C, 68,863 (SD=7,853), 1,035N (SD=120N) respectively. Group C had a statistically significant difference from Group A and Group B in both force of load and cycles loaded. Group A and Group B were not statistically significant from each other.

Conclusions: The fatigue strength of the fixed partial denture is significantly effected by the length of the cantilever. Within the limitations of this investigation, it was found that there is no significant difference between placing a 8 mm or a 10.5 mm (from the center of the proximal screw) cantilever from a two implant supported fixed partial denture. This may impact the use of cantilevers in clinical practice.

Disclosure Statement:
The submitter must disclose the names of the organizations with which any author have a relationship, the nature of the relationship, and the clinical or research area involved. The following is submitted: NONE